I have never been to Los Angeles and so decline to speculate about how superficial the place is. Still, I do think that this reference is innocent and does not betray any particular SoCal esthetic of superficiality. First, I'm used to thinking of petiteness as a polite euphemism for shortness, rather than thinness or shortness plus thinness. After all, petite dress departments usually run in almost the same range as regular ones (up to 12 or 14) and cater to women within a wide range of body mass indexes. I'm curious if others prone to overanalyzing shortness see this differently, though.
I am not sure that anyone has ever liked me for being short. That is probably more because I am good at alienating and offending people of all heights than because of anything else. Nor do most women find shortness in and of itself especially aesthetically appealing. So I suspect that this is an attempt at literary flourish, at sketching a physical description, that just came out kind of oddly.